In electrical systems where signals are transferred from one instrument to another, a data transfer wiring system known as a data bus wiring system may be used.
Those complex systems depend on electronic instruments to determine a condition or a set of conditions, and then transmit information or receive signals about the information over electronic wiring. Such a system is found in "fly-by-wire" aircraft systems where instruments detect various conditions of the aircraft and process the information to control the flight of the aircraft. To transfer the various signals from one instrument to another, a data bus wiring system is used.
A twisted pair of insulated conductors can be used as the data bus. However, while some areas along the length of the data bus must be unshielded so that "stub" cables to and from the instruments can be coupled to the bus, other areas along the bus must be shielded to prevent electrical signals from being radiated or from being subjected to outside noise. However, shielding causes a change in the size, weight, flexibility and electrical properties of the twisted pair data bus. For example, shielding lowers the impedance in that area of the cable and adversely affects performance of the system.